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|

|       x_ovfl.sa 3.5 7/1/91

|

|       fpsp_ovfl --- FPSP handler for overflow exception

|

|       Overflow occurs when a floating-point intermediate result is

|       too large to be represented in a floating-point data register,

|       or when storing to memory, the contents of a floating-point

|       data register are too large to be represented in the

|       destination format.

|

| Trap disabled results

|

| If the instruction is move_out, then garbage is stored in the

| destination.  If the instruction is not move_out, then the

| destination is not affected.  For 68881 compatibility, the

| following values should be stored at the destination, based

| on the current rounding mode:

|

|  RN   Infinity with the sign of the intermediate result.

|  RZ   Largest magnitude number, with the sign of the

|       intermediate result.

|  RM   For pos overflow, the largest pos number. For neg overflow,

|       -infinity

|  RP   For pos overflow, +infinity. For neg overflow, the largest

|       neg number

|

| Trap enabled results

| All trap disabled code applies.  In addition the exceptional

| operand needs to be made available to the users exception handler

| with a bias of $6000 subtracted from the exponent.

|

|

|               Copyright (C) Motorola, Inc. 1990

|                       All Rights Reserved

|

|       THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA

|       The copyright notice above does not evidence any

|       actual or intended publication of such source code.

X_OVFL: |idnt    2,1 | Motorola 040 Floating Point Software Package

        |section        8

        .include "fpsp.h"

        |xref   ovf_r_x2

        |xref   ovf_r_x3

        |xref   store

        |xref   real_ovfl

        |xref   real_inex

        |xref   fpsp_done

        |xref   g_opcls

        |xref   b1238_fix

        .global fpsp_ovfl

fpsp_ovfl:

        link            %a6,#-LOCAL_SIZE

        fsave           -(%a7)

        moveml          %d0-%d1/%a0-%a1,USER_DA(%a6)

        fmovemx %fp0-%fp3,USER_FP0(%a6)

        fmoveml %fpcr/%fpsr/%fpiar,USER_FPCR(%a6)

|

|       The 040 doesn't set the AINEX bit in the FPSR, the following

|       line temporarily rectifies this error.

|

        bsetb   #ainex_bit,FPSR_AEXCEPT(%a6)

|

        bsrl    ovf_adj         |denormalize, round & store interm op

|

|       if overflow traps not enabled check for inexact exception

|

        btstb   #ovfl_bit,FPCR_ENABLE(%a6)

        beqs    ck_inex

|

        btstb           #E3,E_BYTE(%a6)

        beqs            no_e3_1

        bfextu          CMDREG3B(%a6){#6:#3},%d0        |get dest reg no

        bclrb           %d0,FPR_DIRTY_BITS(%a6) |clr dest dirty bit

        bsrl            b1238_fix

        movel           USER_FPSR(%a6),FPSR_SHADOW(%a6)

        orl             #sx_mask,E_BYTE(%a6)

no_e3_1:

        moveml          USER_DA(%a6),%d0-%d1/%a0-%a1

        fmovemx USER_FP0(%a6),%fp0-%fp3

        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar

        frestore        (%a7)+

        unlk            %a6

        bral            real_ovfl

|

| It is possible to have either inex2 or inex1 exceptions with the

| ovfl.  If the inex enable bit is set in the FPCR, and either

| inex2 or inex1 occurred, we must clean up and branch to the

| real inex handler.

|

ck_inex:

|       move.b          FPCR_ENABLE(%a6),%d0

|       and.b           FPSR_EXCEPT(%a6),%d0

|       andi.b          #$3,%d0

        btstb           #inex2_bit,FPCR_ENABLE(%a6)

        beqs            ovfl_exit

|

| Inexact enabled and reported, and we must take an inexact exception.

|

take_inex:

        btstb           #E3,E_BYTE(%a6)

        beqs            no_e3_2

        bfextu          CMDREG3B(%a6){#6:#3},%d0        |get dest reg no

        bclrb           %d0,FPR_DIRTY_BITS(%a6) |clr dest dirty bit

        bsrl            b1238_fix

        movel           USER_FPSR(%a6),FPSR_SHADOW(%a6)

        orl             #sx_mask,E_BYTE(%a6)

no_e3_2:

        moveb           #INEX_VEC,EXC_VEC+1(%a6)

        moveml          USER_DA(%a6),%d0-%d1/%a0-%a1

        fmovemx USER_FP0(%a6),%fp0-%fp3

        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar

        frestore        (%a7)+

        unlk            %a6

        bral            real_inex

ovfl_exit:

        bclrb   #E3,E_BYTE(%a6) |test and clear E3 bit

        beqs    e1_set

|

| Clear dirty bit on dest resister in the frame before branching

| to b1238_fix.

|

        bfextu          CMDREG3B(%a6){#6:#3},%d0        |get dest reg no

        bclrb           %d0,FPR_DIRTY_BITS(%a6) |clr dest dirty bit

        bsrl            b1238_fix               |test for bug1238 case

        movel           USER_FPSR(%a6),FPSR_SHADOW(%a6)

        orl             #sx_mask,E_BYTE(%a6)

        moveml          USER_DA(%a6),%d0-%d1/%a0-%a1

        fmovemx USER_FP0(%a6),%fp0-%fp3

        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar

        frestore        (%a7)+

        unlk            %a6

        bral            fpsp_done

e1_set:

        moveml          USER_DA(%a6),%d0-%d1/%a0-%a1

        fmovemx USER_FP0(%a6),%fp0-%fp3

        fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar

        unlk            %a6

        bral            fpsp_done

|

|       ovf_adj

|

ovf_adj:

|

| Have a0 point to the correct operand.

|

        btstb   #E3,E_BYTE(%a6) |test E3 bit

        beqs    ovf_e1

        lea     WBTEMP(%a6),%a0

        bras    ovf_com

ovf_e1:

        lea     ETEMP(%a6),%a0

ovf_com:

        bclrb   #sign_bit,LOCAL_EX(%a0)

        sne     LOCAL_SGN(%a0)

        bsrl    g_opcls         |returns opclass in d0

        cmpiw   #3,%d0          |check for opclass3

        bnes    not_opc011

|

| FPSR_CC is saved and restored because ovf_r_x3 affects it. The

| CCs are defined to be 'not affected' for the opclass3 instruction.

|

        moveb   FPSR_CC(%a6),L_SCR1(%a6)

        bsrl    ovf_r_x3        |returns a0 pointing to result

        moveb   L_SCR1(%a6),FPSR_CC(%a6)

        bral    store           |stores to memory or register

not_opc011:

        bsrl    ovf_r_x2        |returns a0 pointing to result

        bral    store           |stores to memory or register

        |end